Chemical-Resistant Quartz-Based Casting Composition

ABSTRACT

A quartz-based casting composition provides excellent resistance to attack by chemicals, including weak and strong acids. The quartz-based casting composition is useful as concrete in various construction applications where corrosion resistance is needed. The casting composition includes a dry component and a wet component. The dry component includes about 25% to about 100% by weight quartz and the corrosion resistance increases with increasing quartz content.

FIELD OF THE INVENTION

This invention is directed to a chemical-resistant quartz-based castingcomposition that can be used as concrete for construction in corrosiveenvironments.

BACKGROUND OF THE INVENTION

In recent years, efforts to develop chemically inert and chemicallyresistant concrete compositions have moved toward center stage in theconstruction industry. These compositions are useful in a wide varietyof construction applications, especially industrial construction wheredirect or occasional exposure to acids and other corrosive chemicals isencountered. Examples of corrosive environments include wastewatertreatment plants, manholes, chemical plants, oil refineries, pulp andpaper plants, sulfur pits, sumps, industrial and garage floors, roofs,drains, gutters, pipes, sewers and trenches.

U.S. Pat. No. 9,822,038, issued to Paulter et al., discloses achemically inter concrete composition that includes, by dry weight,about 50% to about 95% by weight glass particles and about 3% to about40% by weight colloidal silica particles, and is substantially ortotally free of conventional cement. Conventional cement, such asPortland cement, is not only vulnerable in corrosive environments, butalso contains caustic elements such as Group I and Group II metal oxidesthat can cause irritation and burns to a user's skin. The glass-basedand colloidal silica-based composition disclosed in the foregoing patentto Paulter et al. eliminates these corrosive elements and is chemicallyinert to most acids (except hydrofluoric acid) and most other chemicals.U.S. Pat. No. 10,577,280, also issued to Paulter et al, is directed to acorresponding method of providing chemically inert concrete.

Calcium aluminate-based cements have been developed which providesomewhat improved chemical resistance over Portland cement. However, thechemical resistance of the calcium aluminate-based cements is generallylimited to a pH of about 3.5-4.0 or higher. These cements generally donot perform well in stronger acidic environments that result in exposureto lower pH's.

U.S. Pat. No. 8,137,434, issued to McPherson, discloses a cementcomposition that includes at least 60% by weight fine or coarse glassaggregate. That composition also includes required amounts of Portlandcement which is not chemically inert. Only a small amount of corrosionand degradation will adversely affect the performance of a concreteconstruction material.

There is a need or desire for a castable concrete composition thatresists attack by both strong and weak acids over long periods of time,and which is suitable for construction and long-term use in high-stresscorrosive environments.

SUMMARY OF THE INVENTION

The present invention is directed to a quartz-based casting compositionthat includes a dry component and a wet component. The dry componentincludes from about 25% to about 100% by weight quartz and the wetcomponent includes an aqueous colloidal silica binder. The inventionincludes a high-performance embodiment and a lower cost embodiment. Thehigh-performance embodiment includes a higher amount of quartz in thedry component than the lower cost embodiment. The casting composition ofthe invention is useful as a concrete for various constructionapplications in which resistance to strong and weak acids and otherchemical exposure is needed. These applications include withoutlimitation wastewater treatment plants, manholes, chemical plants, oilrefineries, pulp and paper plants, sulfur pits, sumps, industrial andgarage floors, roofs, drains, gutters, pipes, sewers and trenches.

In one embodiment, the invention is directed to a quartz-based castingcomposition that includes a dry component and a wet component;

the dry component including about 25% to about 100% by weight quartz,zero to about 25% by weight gravel and zero to about 50% by weightconcrete sand;

the wet component including about 30% to about 60% by weight colloidalsilica particles and about 40% to about 70% by weight water;

wherein the quartz-based casting composition includes about 65% to about97% by weight of the dry component and about 3% to about 35% by weightof the wet component.

In another embodiment, the invention is directed to a quartz-basedcasting composition including a dry component and a wet component;

the dry component including at least about 85% by weight quartz andoptionally at least about 1% by weight microsilica;

the wet component including about 30% to about 60% by weight colloidalsilica particles and about 40% to about 70% by weight water;

wherein the quartz-based casting composition includes about 65% to about97% by weight of the dry component and about 3% to about 35% by weightof the wet component.

In another embodiment, the invention is directed to a quartz-basedcasting composition including a dry component and a wet component;

the dry component including about 25% to about 40% by weight quartz,about 10% to about 30% by weight gravel, and about 35% to about 50% byweight concrete sand;

the wet component including about 30% to about 60% by weight colloidalsilica particles and about 40% to about 70% by weight water;

wherein the quartz-based casting composition includes about 65% to about97% by weight of the dry component and about 3% to about 35% by weightof the wet component.

With the foregoing in mind, it is a feature and advantage of theinvention to provide a chemical-resistant quartz-based castingcomposition that provides resistance to strong acids, weak acids andother chemicals in corrosive environments.

It is also a feature and advantage of the invention to provide achemical-resistant, quartz-based casting composition that is useful inthe construction of wastewater treatment plants, manholes, chemicalplants, oil refineries, pulp and paper plants, sulfur pits, sumps,industrial and garage floors, roofs, drains, gutters, pipes, sewers andtrenches.

It is also a feature and advantage of the invention to provide a methodof making a chemical-resistant quartz-based concrete structure.

These and other features and advantages of the invention will becomefurther apparent from the following detailed description of theinvention, read in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bar graph showing mass loss of concrete blocks made from theinventive high-performance chemical-resistant quartz-based castingcomposition, the inventive lower cost quartz-based casting composition,and three commercially available concrete compositions after seven daysand 28 days in a 15% sulfuric acid solution.

FIG. 2 shows photographs of concrete blocks formed from the inventivehigh-performance chemical-resistant quartz-based casting composition,the inventive lower cost quartz-based casting composition, and threecommercially available concrete compositions after seven days in a 15%sulfuric acid solution.

FIG. 3 shows photographs of concrete blocks formed from the inventivehigh-performance chemical-resistant quartz-based casting composition andfrom four commercially available concrete compositions after 28 days ina 15% sulfuric acid solution.

DETAILED DESCRIPTION OF THE INVENTION

The invention is directed to a quartz-based casting composition havingexcellent chemical resistance in a corrosive environment and a method ofmaking a chemical-resistant quartz-based concrete. The quartz-basedcasting composition includes a dry component and a wet component. Thedry component includes about 25% to about 100% by weight quartz, zero toabout 50% by weight gravel, and zero to about 50% by weight concretesand. The wet component includes about 30% to about 60% by weightcolloidal silica particles and about 40% to about 70% by weight water.The quartz-based casting composition can include about 65% to about 97%by weight of the dry component, suitably about 75% to about 95% byweight of the dry component, or about 85% to about 93% by weight of thedry component. The quartz-based casting composition can include about 3%to about 35% by weight of the wet component, suitably about 5% to about25% by weight of the wet component, or about 7% to about 15% by weightof the wet component.

The quartz-based casting composition includes a high-performance, highercost embodiment in which the dry component includes higher percentagesof quartz, and a suitable lower cost embodiment in which the drycomponent includes lower percentages of quartz mixed with sand andgravel. In the high-performance embodiment, the dry component caninclude at least about 50% by weight quartz, suitably at least about 75%by weight quartz, or at least about 85% by weight quartz, or at leastabout 90% by weight quartz, or at least about 95% by weight quartz, andcan include up to about 100% by weight quartz, or up to about 99% byweight quartz, or up to about 98% by weight quartz, or up to about 97%by weight quartz, or up to about 96% by weight quartz, or up to about95% by weight quartz. For example, the dry component can include about50% to about 99% by weight quartz, or about 75% to about 98% by weightquartz, or about 85% to about 97% by weight quartz, or about 90% toabout 97% by weight quartz. The dry component of the high-performanceembodiment can optionally include at least about 1% by weightmicrosilica, or at least about 2% by weight microsilica, or at leastabout 3% by weight microsilica, and can include up to about 25% byweight microsilica, or up to about 15% by weight microsilica, or up toabout 10% by weight microsilica, or up to about 5% by weightmicrosilica. In one embodiment, the quartz and the optional microsilica(if present) constitute about 90-100% by weight, or about 95-99% byweight of the dry component. The optional microsilica aids the flow ofthe quartz-based casting composition and reduces the porosity (and thus,the exposed surface area) of a concrete structure made from thequartz-based casting composition.

The particle size distribution of the quartz can also be tailored toyield a solid, compact high-performance concrete structures with minimalporosity. In one embodiment, the overall quartz can have a particle sizedistribution in which about 10-35% by weight of the quartz, suitablyabout 15-25% by weight of the quartz, has a particle size ranging from0.5 inch to 6 mesh (12,700 to 3360 microns); about 20-45% by weight,suitably about 25-35% by weight of the quartz has a particle sizeranging from under 6 mesh to 20 mesh (less than 3360 to 841 microns);about 5-25% by weight of the quartz, suitably about 10-20% by weight ofthe quartz has a particle size ranging from under 20 mesh to 50 mesh(less than 841 to 297 microns); about 5-25% by weight, suitably about10-20% by weight of the quartz has a particle size ranging from under 50mesh to 100 mesh (less than 297 to 149 microns); and about 15-35% byweight, suitably about 10-20% by weight of the quartz has a particlesize of under 100 mesh (less than 149 microns).

The foregoing size distribution can be achieved by blending togethercommercially available quartz grades having known size distributions. Inone embodiment, the above particle size distribution can be achieved byblending about 5-20% by weight of a quartz having a particle size ofabout 0.5 inch to 8 mesh (12,700 to 2380 microns), about 15-35% byweight of a quartz having a particle size of about 4 to 16 mesh (4760 to1190 microns), about 5-20% by weight of a quartz having a particle sizeof about 12 to 25 mesh (1680 to 707 microns), about 2-15% by weight of aquartz having a particle size of about 20 to 50 mesh (841 to 297microns) and about 20-50% by weight of a quartz has particle size ofabout 140 mesh to greater than 325 mesh (105 to less than 44 microns).Commercially available grades of quartz that meet these descriptions areavailable from Agsco Corporation of Wheeling, Ill. Suitable Agsco quartzgrades include Quartz #10 (0.5 in. to 8 mesh), Quartz ¼×⅛ (4 to 16mesh), Quartz #5 (5 to 14 mesh), Quartz #4 (12 to 25 mesh), Quartz #3(20 to 50 mesh), Quartz #3/0 (140 to smaller than 325 mesh) and Quartz#4/0 (170 to smaller than 325 mesh).

The dry component of the high performance, quartz-based castingcomposition can also include about 0.01 to about 1% by weight of asetting agent, suitably about 0.1 to about 0.3% by weight of a settingagent. One exemplary setting agent is magnesium oxide. The dry componentcan also include about 0.01 to about 0.5% by weight of one or moredispersants, suitably about 0.01 to about 0.05% by weight of one or moredispersants. Exemplary dispersants include without limitationphosphonate dispersants available from Italmatch Chemicals and polyaciddispersants available from Dow Chemical Co.

The dry component of the lower cost quartz-based casting compositionincludes less quartz, and the quartz is mixed with concrete sand and/orgravel. Concrete sand is an aggregate sand that is usually composed ofgneiss, trap rock, limestone and/or granite. This type of sand isnormally crushed in a quarry and then washed and screened for quality.This process ensures that there are no large rocks in the material. Onesuitable gravel is Gravel #8, available from Kurtz Bros., Inc., andvarious other suppliers. Gravel #8, also called Pea Gravel, is a mixtureof small particles of river rock which can range in size from ⅛ inch to⅜ inch. Gravel #8 is light in color, a blend of different colors, and istypically washed and screened to remove large rocks.

The dry component of the lower-cost embodiment can include from about25% to about 50% by weight quartz, about 10% to about 35% by weightgravel and about 30% to about 55% by weight concrete sand. Suitably, thedry component may contain about 25% to about 40% by weight quartz, orabout 25% to about 35% by weight quartz; about 10% to about 30% byweight gravel, or about 15% to about 25% by weight gravel; and about 35%to about 50% by weight concrete sand, or about 40% to about 50% byweight concrete sand. Quartz is the primary element for providing thecasting composition and ultimate concrete structure with chemicalresistance and is also the primary driver of cost. Therefore, the lowerthe quartz content, the lower the cost and chemical resistance. Thehigher the quartz content, the higher the cost and chemical resistance.The lower-cost embodiment can also have a quartz content whose sizedistribution is tailored as described with respect to thehigh-performance embodiment described above, or a size distribution thatis not tailored. In one embodiment, the size distribution of the quartzis not tailored and only one grade of quartz is used. One suitablequartz for the lower cost embodiment is Agsco Quartz #4/0, descriedabove, which has a size distribution ranging from about 170 to greaterthan 325 mesh (88 to less than 44 microns).

The elements of the dry component can be mixed together using a drumtumbler, hopper blender or other suitable dry mixer. The dry componentcan be combined with the wet component either a) simultaneously with themixing of the dry component ingredients, or preferably b) separately, asdescribed below, after both the dry component and the wet component havebeen separately prepared. The ingredients of the wet component are thesame for both the high-performance quartz-based casting composition andthe lower cost quartz-based casting composition. The wet componentincludes an aqueous colloidal silica suspension. The colloidalsuspension can include about 40% to about 70% by weight water and about30% to about 60% by weight colloidal silica particles, suitably about50% to about 60% by weight water and about 40% to about 50% by weightcolloidal silica particles. The colloidal silica particles have aparticle size range that facilitates the formation of a colloidalsuspension, and typically have a size ranging between about 1 and about100 nanometers.

The separately prepared dry component and wet component can be combinedtogether in a concrete mixer or other suitable mixer to form a dampslurry which can then be cast into a final concrete structure and dried,with or without heat, to form a solid chemical-resistant concrete objector layer. The castable quartz-based composition can be cast into a moldto form a concrete shape (object or block) or can be cast onto a flat orcurved substrate surface to form a shaped concrete layer. The concreteshape can then be dried at ambient or elevated temperature (e.g., 230°F.) to form a concrete structure. The concrete structure (block, part orlayer) can be in an environment where chemical attack might otherwisepresent a problem over time. Examples include without limitationconcrete structures for chemical plants, oil refineries, pulp and paperplants, wastewater treatment plants, sulfur pits, manholes, sumps,floors, roofs, drains, gutters, pipes, sewers, trenches, industrial andgarage floors, and other corrosive environments.

Examples 1-4

Four samples of inventive quartz-based castable compositions wereprepared as damp slurries having the following ingredients (see Table 1below). The first two samples were high-performance quartz-based castingcompositions, while the third and fourth were lower-cost quartz-basedcasting compositions, as described in Table 1 below. The four castablecompositions were formed into rectangular concrete blocks and dried to atemperature of 230° F. For the cold crushing strength test describedbelow (ASTM C133), the blocks had dimensions of 2-inch×2-inch×2-inch.Rectangular blocks having dimensions of 8-inch×1.5-inch×1.5-inch wereused for the other tests. The rectangular concrete blocks were thentested according to the procedures described below to yield theproperties indicated in Table 1 below.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Ingredient Gravel #8  20%   20% Concrete Sand   47%   47% Quartz #10 12.1% 12.7% Quartz ¼ ×⅛ 15.2% 15.9% Quartz #5 12.1% 12.7% Quartz #4 12.1% 12.7% Quartz #3 9.1% 12.7% Quartz #3/0  7.6% Quartz #4/0 28.0% 29.5% 29.5% 29.5%Microsilica  3.8%  3.8%  3.8%  3.8% MgO 0.15% 0.15% 0.15% 0.15%Phosphonate Dispersant 0.02% 0.02% 0.02% 0.02% Polyacid Dispersant0.005%  0.005%  0.005%  0.005%  Total Dry Comp.  100%  100%.  100%. 100%. Dry Component 100 parts by wt. 100 parts by wt. 100 parts by wt.100 parts by wt. in Composition Colloidal Silica  100%  100%  100%  100%(40% in Water) Wet Component 9 parts by wt. 9 parts by wt. 11 parts bywt. 15 parts by wt. in Composition Properties Flow - ASTM 15   14    2 58 C-1445 Cold Crushing 4547 psi 4989 psi 5200 psi 4060 psi Strength-ASTM C133, 230° F. Cold Crushing 5023 psi 4677 psi 6020 psi 5090 psiStrength- ASTM C133, 800° F. Density - ASTM 141 pcf 142 pcf 137 pcf 136pcf C20, 230° F. Density - ASTM 140 pcf 142 pcf 137 pcf 133 pcf C20,800° F. Porosity- ASTM 13.2% 12.4% 17.4% 18.3% C20, 230° F. Porosity-ASTM 13.0% 12.4% 18.0% 20.2% C20, 800° F. Quartz Size Distribution, %12,700 to 3360 20.99 21.99 microns less than 3360 to 30.39 31.96 841microns less than 841 to 12.33 15.94 297 microns less than 297 to 12.08 7.88 149 microns less than 149 24.23 22.23 100 100 microns

As shown above, the concrete samples made from high-performancequartz-based casting compositions of Examples 1 and 2 had less porosityand higher density compared to the lower cost quartz-based castingcompositions of Examples 3 and 4. Low porosity aids chemical resistanceby reducing the surface area available for exposure to chemicals. Allthe concrete samples had high cold crushing strength.

The concrete blocks from Examples 1-4 were tested for exposure toconcentrated (78%) boiling aqueous sulfuric acid for a period of 48hours using the procedure set forth in ASTM C-279. The concrete blocksfrom Examples 1 and 2 showed an average weight loss of 0.4%, which isexcellent compared to competitive concrete compositions. The concreteblocks from Examples 3 and 4 showed an average weight loss of 8.54%,which is good compared to competitive concrete compositions.

Examples 5-9

For Example 5, the two 2-inch×2-inch×2-inch concrete blocks as describedin Examples 1 and 2 were used and the results below were averaged. Themolded composition was dried at a temperature of 230° F. to form theconcrete blocks.

For Example 6, two 2-inch×2-inch×2-inch concrete blocks as described inExamples 3 and 4 were used and the results below were averaged. Themolded composition was dried at a temperature of 230° F. to form theconcrete blocks.

For Example 7, two concrete blocks having the same dimensions as inExamples 5 and 6 were formed using a first competitive concretecomposition which is based primarily on calcium aluminate cement, and isdesigned for coating municipal wastewater structures including manholes,lift stations, wet wells, and the like. The composition was dried atambient temperature to form the concrete blocks.

For Example 8, two concrete blocks having the same dimensions as inExample 5 and 6 were formed using a second competitive concretecomposition which is based primarily on a modified calcium aluminatecement designed for installation by the gunite method, and is used forlining industrial chimneys, stacks and ductwork, incinerator quenchchambers, molten sulfur pit linings and sulfur recovery units. Thecomposition was dried at 230° F. to form the concrete blocks.

For Example 9, two concrete blocks having the same dimensions as inExample 5 and 6 were formed using a third competitive concretecomposition which is a high-strength concrete mix used for driveways,sign footings, patios, deck supports, curbs and floors. The compositionwas dried at ambient temperature to form the concrete blocks.

The concrete blocks of Examples 5-9 were immersed in 15% aqueoussulfuric acid. The samples were weighed before testing and after 7 daysand 28 days to determine weight loss resulting from the acid exposure.FIG. 1 is a bar graph that shows the results of the testing. Thehigh-performance quartz-based concrete blocks of Example 5 outperformedthe competitive concrete blocks of Examples 7-9 by a wide margin,yielding zero or negligible weight loss at 7 days and 28 days. The lowercost quartz-based concrete blocks of Example 6 yielded the second-bestperformance with average weight losses of 1% after 7 days and 8% after28 days. The calcium aluminate cement-based concrete of Example 7 showed4% weight loss after 7 days and much higher 18% weight loss after 28days in the sulfuric acid. The high-strength concrete composition ofExample 9 showed a modest 7% weight loss after 7 days and 12% weightloss after 28 days. The modified calcium aluminate cement composition ofExample 8 mostly dissolved in the sulfuric acid, showing a 61% weightloss after 7 days and an 81% weight loss after 28 days.

FIGS. 2 and 3 include photographs of the concrete blocks of Examples5-9, taken after 7 and 28 days in the sulfuric acid. The concrete blocksmade from the high-performance quartz-based compositions (Example 5)showed no damage after 7 and 28 days. The concrete blocks made from thelower cost quartz-based compositions (Example 6) showed negligibledamage after 7 days and more noticeable damage after 28 days. Theremaining concrete blocks of Examples 7-9 showed substantial damage fromdissolution and weight loss after 7 days, and even more damage after 28days.

The embodiments of the invention described herein are exemplary. Variousmodifications and improvements can be made without changing the spiritand scope of the invention. The scope of the invention is indicated bythe appended claims, and all changes that fall within the meaning andscope of equivalents are intended to be embraced therein.

We claim:
 1. A quartz-based casting composition, comprising a drycomponent and a wet component; the dry component including about 25% toabout 100% by weight quartz, zero to about 25% by weight gravel and zeroto about 50% by weight concrete sand; the wet component including about30% to about 60% by weight colloidal silica particles and about 40% toabout 70% by weight water; wherein the quartz-based casting compositionincludes about 65% to about 97% by weight of the dry component and about3% to about 35% by weight of the wet component.
 2. The quartz-basedcasting composition of claim 1, comprising about 75% to about 95% byweight of the dry component and about 5% to about 25% by weight of thewet component.
 3. The quartz-based casting composition of claim 1,wherein the dry component further comprises about 1% to about 10% byweight microsilica.
 4. The quartz-based casting composition of claim 2,wherein the dry component comprises about 2% to about 5% by weight ofthe microsilica.
 5. The quartz-based casting composition of claim 1,wherein the colloidal silica has a median particle diameter of about1-100 nanometers.
 6. The quartz-based casting composition of claim 1,wherein the dry component includes about 50% to about 99% by weightquartz.
 7. The quartz-based casting composition of claim 6, wherein thequartz has a size distribution such that about 10-35% by weight of thequartz has a particle size ranging from 0.5 inch to 6 mesh (12,700 to3360 microns), about 20-45% by weight of the quartz has a particle sizeranging from under 6 mesh to 20 mesh (less than 3360 to 841 microns),about 5-25% by weight of the quartz has a particle size ranging fromunder 20 mesh to 50 mesh (less than 841 to 297 microns), about 5-25% byweight of the quartz has a particle size ranging from under 50 mesh to100 mesh (less than 297 to 149 microns), and about 15-35% by weight ofthe quartz has a particle size of under 100 mesh (less than 149microns).
 8. The quartz-based casting composition of claim 1, whereinthe dry component includes about 75% to about 98% by weight quartz. 9.The quartz-based casting composition of claim 1, wherein the drycomponent includes about 90% to about 97% by weight quartz.
 10. Thequartz-based casting composition of claim 1, wherein the dry componentincludes about 25% to about 50% by weight quartz, about 10% to about 35%by weight gravel, and about 30% to about 55% by weight concrete sand.11. The quartz-based casting composition of claim 10, wherein the quartzhas a particle size of about 88 to less than 44 microns.
 12. Aquartz-based casting composition, comprising a dry component and a wetcomponent; the dry component including at least about 85% by weightquartz and optionally at least about 1% by weight microsilica; the wetcomponent including about 30% to about 60% by weight colloidal silicaparticles and about 40% to about 70% by weight water; wherein thequartz-based casting composition includes about 65% to about 97% byweight of the dry component and about 3% to about 35% by weight of thewet component.
 13. The quartz-based casting composition of claim 12,wherein the dry component includes at least about 90% by weight quartzand at least about 2% by weight microsilica.
 14. The quartz-basedcasting composition of claim 12, wherein the dry component includes atleast about 95% by weight quartz and at least about 3% by weightmicrosilica.
 15. The quartz-based casting composition of claim 12,wherein the quartz has a size distribution such that about 10-35% byweight of the quartz has a particle size ranging from 0.5 inch to 6 mesh(12,700 to 3360 microns), about 20-45% by weight of the quartz has aparticle size ranging from under 6 mesh to 20 mesh (less than 3360 to841 microns), about 5-25% by weight of the quartz has a particle sizeranging from under 20 mesh to 50 mesh (less than 841 to 297 microns),about 5-25% by weight of the quartz has a particle size ranging fromunder 50 mesh to 100 mesh (less than 297 to 149 microns), and about15-35% by weight of the quartz has a particle size of under 100 mesh(less than 149 microns).
 16. The quartz-based casting composition ofclaim 12, comprising about 75% to about 95% by weight of the drycomponent and about 5% to about 25% by weight of the wet component. 17.A quartz-based casting composition, comprising a dry component and a wetcomponent; the dry component including about 25% to about 40% by weightquartz, about 10% to about 30% by weight gravel, and about 35% to about50% by weight concrete sand; the wet component including about 30% toabout 60% by weight colloidal silica particles and about 40% to about70% by weight water; wherein the quartz-based casting compositionincludes about 65% to about 97% by weight of the dry component and about3% to about 35% by weight of the wet component.
 18. The quartz-basedcasting composition of claim 17, wherein the dry component comprisesabout 25% to about 35% by weight quartz, about 15% to about 25% byweight gravel, and about 40% to about 50% by weight concrete sand. 19.The quartz-based casting composition of claim 18, wherein the quartz hasa particle size of about 88 to less than 44 microns.
 20. Thequartz-based casting composition of claim 17, comprising about 75% toabout 95% by weight of the dry component and about 5% to about 25% byweight of the wet component.